Druse:
Sow outdoors in Fall, or sow indoors 70-75F for germination in 7-14 days.

plants.usda.gov:
buttonbush seeds are ready for collection in the fall when they have turned reddish-brown. No pretreatment is necessary. Sow seeds into moist, humus soils in full sun or part shade.

Clothiers:
Cephalanthus occidentalis , Buttonbush ,zone= 5 , sow @ 70ºF

Mine have had high germination rates, typically about 70+%, but I used "Byron's Tea Recipe" to start the last batch. It went up to maybe 80+%. Sow them early spring or fall. I start them in small pots, but you can direct sow. They get rather big though; so sowing in pots is better I think.

I just started some seeds indoors. What is the growth rate from seed? Will I have a bush by fall? Im looking at transplanting some around a duck hole by October.

Thanks in advance